High Temperature C₃H₆/C₃H₈ Separation through Silica Hybrid Membranes

Abstract

Silica-organic hybrid membranes were successfully prepared on -alumina substrates by using a counter diffusion CVD method. Propyltrimethoxysilane (PrTMOS) was employed as a silica source, and O 3 was used as a reactant. Deposition temperatures of the CVD were very important parameters for the membrane properties. C 3 H 6 /C 3 H 8 peremeance ratio was 12.1 at 320 through a membrane prepared at 320 . C 3 H 6 /C 3 H 8 peremeance ratios were proportional to N 2 /SF 6 permeance ratios showing that the C 3 H 6 /C 3 H 8 selectivity are due to a molecular sieving mechanism. The decomposition mechanism of propyl groups on silica surface was discussed by using powders prepared by hydrolysis of PrTMOS. Propyl groups were partially decomposed under 320 of an O 3 atmosphere. This indicates that the obtained membrane was a silica-organic hybrid membrane.

Organic–Inorganic Hybrid Silica Membranes with Controlled Silica Network Size for Propylene/Propane Separation

“…The order of gas permeances for BTESM-derived silica membranes was C 3 H 6 > C 3 H 8 , independent of the number of sol coats and temperature (50–200 °C), although the kinetic diameter of C 3 H 6 ( d k = 0.45 nm) is reported to be larger than that of C 3 H 8 ( d k = 0.43 nm) . To date, only a few papers , have reported on the single gas permeation properties of C 3 H 6 and C 3 H 8 molecules above 200 °C, where molecular sieving can be dominant, which is quite important to a discussion of the effective molecular size of these molecules through a membrane. Sea et al first reported on C 3 H 6 and C 3 H 8 permeation properties above 200 °C through a silica membrane prepared by the CVD method.…”

“…Thus, it is quite difficult to discuss the effective molecular size of C3 hydrocarbons for this membrane. Nomura et al successfully fabricated silica–organic hybrid membranes by a counterdiffusion CVD method using propyltrimethoxysilane (PrTMOS). These membranes showed a C 3 H 6 /C 3 H 8 permeance ratio of 12.1 at 320 °C, and the C 3 H 6 /C 3 H 8 permeance ratios were proportional to the N 2 /SF 6 permeance ratios, so the authors concluded that the C 3 H 6 /C 3 H 8 selectivity could be ascribed to the molecular sieving mechanism, which is consistent with our results.…”

“…Figure shows the C 3 H 6 /C 3 H 8 selectivity for carbon-derived, − zeolite-derived, − silica (TEOS, PrTMOS)-derived, , and BTESM-derived membranes as a function of C 3 H 6 permeances. Generally, membranes with high selectivity show low permeance, due to the trade-off relationship.…”

“…C 3 H 6 /C 3 H 8 separation performance for SiO 2 membranes , was scattered, probably because it is quite difficult to control the appropriate pore size for separation of C 3 H 6 and C 3 H 8 molecules. BTESM-derived silica membranes showed superior C 3 H 6 permeance with high C 3 H 6 /C 3 H 8 selectivity in a wide temperature range (50–200 °C).…”

Propylene/propane Permeation Properties of Metal-doped Organosilica Membranes with Controlled Network Sizes and Adsorptive Properties

“…, zeolite 8) 10) , ZIF-8 (ZIF-8, Zn(MeIM)2, MeIM: 2-methylimidazole) 11) 15) and amorphous silica 16) 19) , and separation properties of olefin from paraffin that strongly depended on the separation conditions (temperature, pressure and feed concentration). Those published papers suggest the importance of tailoring the pore size for improved molecular sieving separation, and controlling the adsorptive properties, particularly for olefin molecules.…”